Method of and material for treating metal



Patented July 23, 1935 2,008,939 I UNITED STATES PATENT OFFICE METHOD OF AND MATERIAL FOR TREATING METAL mm L. Tufts, Worcester, Mass.

No Drawing. Application July 29, 1932, Serial No. 626,211

18 Claims. (Cl. 205--2l) This invention relates to a method of and mamospheric carbonic acid which would otherwise terial for treating metal, and more specifically facilitate metal corrosion. relates to lubricating and cold-working metal, Di-potassium phosphate is more satisfactory removing the lubricant by a simple water rinse, in certain ways than some other phosphates that 5 and applying a permanent finishing coat, and to approach it in desired qualifications in that it 5 a lubricating material suitable for use in carryis somewhat hygroscopic and with concentrated ing out this method. solutions there is less tendency to crystallize.

The permanent finishing coat referred to may Moreover this tendency may be markedly rebe paint, lacquer, enamel, electro-plating or other strained by addition of a suitable inhibiting applied coat, or a phosphate or other chemically agent. 10

formed coat. The materials most nearly analogous in the In cold-working processes, such as machining, physical properties mentioned are mono-sodium drawing, punching, stamping, etc., it has been phosphate and mono-ammonium phosphate, since customary to lubricate the metal with oil, grease they are the most soluble of the ortho phosphates or emulsions thereof. Such a lubricant must be of the respective bases. They do have a slight 15 very thoroughly removed before finishing the suracid reaction, but the small amount of etching face with a permanent coat or remnants of the action-that they may exert under ordinary conoil or grease will interfere with the proper formaditions is not objectionable where painting, laction or binding of the coat. A simple water rinse quering or enamelling constitute the final finish,

to does not remove the greasy lubricant, and proper nor is it undesirable on iron or steel where a final cleaning involves considerable expense and rephosphate coating is to be formed. quires careful work. The metal surface may ap- The sodium and ammonium phosphates are pear bright and clean while retaining sufiicient cheaper than di-potassium phosphate, and may 1 residual grease to interfere with proper finishing. be substituted in whole or in part for the potas- 2; A careful workman may detect such imperfect sium salt for purposes of economy, or where a cleaning by observing what is known as water definite pH value is desired for any purpose, break, that is, when water draining from the any such value between the alkaline value of the surface leaves drops or spots instead of an evenly potassium salt and the acid value of the sodium distributed thin film of water on the surface; but or ammonium salt may be obtained by a proper hurried or careless work may easily result in immixture of the salts. 30 perfect cleaning and consequently inferiority in The efiiciency as lubricants of the highly solthe finished product. uble and highly concentrated salts specified can It may be noted incidentally that ordinary lube increased by addition of small quantities of a brlcating materials frequently contain substances suitable wetting agent. For this purpose, among which may produce insoluble greasy metal soap several available materials, I have preferred to 35 deposits, that increase scouring difiiculty. use sulphonated castor oil soap, since less than On the other hand, where metal working treat- 1% dry basis by weight is sufilcient to obtain the ment isdone according to the present invention, desired results, and it freely blends with the metal products free fromwater break are quicksolution without foaming. Where the material ly available by a simple water rinse. is to be exposed in thin layers under drying con- This ready rinseability may be obtained by ditions that might result in objectionable evapemploying as a lubricant a concentrated aqueous oration, I have used additions of concentrated solution of (ii-potassium phosphate or other highglycerine or diethylene glycol which have proved ly water soluble inorganic salt that is capable of advantageous from this point of view and with 43 attaining a sufiicient oily viscosity for lubricating the former material even up to amounts of 45 purposes. Such a solution may be prepared with 25% by volume. To attain highest viscosities, aviscosity and lubricating character in the neigh-- the glycerine has been added to the highly conborhood of or slightly superior to the highly recentrated solution before cooling. Where an ungarded lubricant, lard oil, and capable of comusually highly bodied lubricant is desired, the

peting in working qualities with this or other concentration of the di-potassium phosphate may similar lubricating products. It is thus adapted be carried to such an extent, before the addition to cold-working of metal with a benefit from its of glycerine, that a finely divided suspended added desirable features. This particular mate-. magma may result in the final solution. Such rial has a slight alkaline reaction which permits material as sulphonated castor oil soap may be it to combine with and neutralize traces of atused in addition to glycerine or the like in the phosphate solution to decrease the drying or crystallizing tendencies without impairing the lubricating efficiency. Trouble from drying out may be avoided by the use of a thinner solution where it will furnish the necessary lubrication.

The slight alkalinity of the di-potassium phosphate leaves the metal in a more rust-resistant condition than would a neutral or acid solution, and additional alkali may be added to the solution, or supplied in the rinse water when the lubricant is removed, if it is desired with any of the solutions mentioned. Additional inhibition of rusting, after removal of the lubricant, may be secured by adding as little as .1% sodium bichromate or other chromate of an alkali metal.

In practice, since this new lubricating material can be washed off with clear water, I am able to readily recover the same, by use of a suitable counter current washing system that includes a slight amount of final concentration, for reuse as lubricant or for other purposes. Where the heat of metal working produces sufiicient evaporation, the lubricant solution direct from the counter current washing may be used as the makeup solution for the lubricant. In any event the nature of the material is not changed by rinsing oil, as is the character and availability of grease or oil when they are washed off with the aid of chemicals or soap.

The alkali phosphate lubricants mentioned above are particularly desirable when working metal that is to have formed on its surface a phosphate coat such as is widely used either as a finishing coat in itself or as a bond for such a finishing coat as paint, lacquer or enamel.

Other inorganic salts have some of the characteristics of the phosphate salts mentioned, and might be used under some circumstances to a probablyquite limited extent, but do not meet the requirements so completely. For example, water glass or silicate of soda has a wide range of concentrations with appreciable viscosity and may be used as a lubricant under some conditions. An important disadvantage is that it acts as an adhesive on drying and must be kept moist to be readily removable.

Under the same classification may be mentioned concentrated solutions such as zinc chloride or aluminum chloride, but for most common metals they are of corrosive nature.

It will be understood that the cold working of the metal may be accomplished in any well known manner, and that the application of the coating for the final cold working may be by any of the customary processes, this invention effecting no changes in these steps per se; yet the beneficial eifects of the use of the new lubricant lie largely in the excellent and stable lubricating qualities combined with the ease and completeness of removal and the consequent uniformity and adhesion of the final finish coat applied.

Some alternatives have been described and specifically claimed, but it is understood that other changes may be made within the scope of the appended claims.

What is claimed is:

1. The method which comprises coating metal with a concentrated aqueous solution of alkali phosphate of the group consisting of dipotassium phosphate, mono-sodium phosphate and monoammonium phosphate, and cold working the metal while lubricated with said solution.

2. The method which consists in coating metal with a concentrated solution of di-potassium phosphate, and cold working the metal while lubricated with said solution.

3. The method which consists in coating metal with a concentrated solution of mono-sodium phosphate, and cold working the metal while lubricated with said phosphate.

4. The method which consists in coating metal with a concentrated solution of mono-ammonium phosphate, and cold working the metal while coated with said phosphate.

5. The method which consists in coating metal with a concentrated aqueous solution of an alkali phosphate having a solubility in water of the order of that of di-potassium phosphate, cold-working the metal while so coated, washing the coating off of the formed metal, and applying a permanent protective coating to the washed surface.

6. The method which consists in coating a metal surface with a. concentrated aqueous solution of a substantially non-corrosive, inorganic, salt having a solubility in water of the order of that of di-potassium phosphate and containing a wetting agent, and cold-working the metal while lubricated by said solution.

7. The method which consists in coating a metal surface with a concentrated aqueous solution of a substantially non-corrosive, inorganic salt having a solubility in water of the order of that of di-potassium phosphate and containing hygroscopicmaterial, and cold-working the metal while lubricated by said solution.

8. The method which consists in coating a metal surface with a concentrated aqueous solution of a substantially non-corrosive, inorganic salt having a solubility in water of the order .of di-potassium phosphate and containing a wetting agent and hygroscopic material, and coldworking the metal while lubricated by said solution.

9. The method which consists in coating metal with a concentrated aqueous solution of an alkali phosphate having a solubility in water'fof the order of that of di-potassium phosphate'arid containing a wetting agent, and cold-working the metal while lubricated with said solution.

10. The method which consists in coating metal with a concentrated aqueous solution of an alkali phosphate having a solubility in water .of the order of that of di-potassium phosphateand containing glycerine, and cold-working the metal while lubricated with said solution.

11. The method which consists in coating metal with a concentrated aqueous solution of a substantially non-corrosive, inorganic salt having.

12. The method which consists in coating metal with a concentrated aqueous solution of an alkali phosphate having a solubility in water of the order of that of di-potassium phosphate and containing a wetting agent, cold-working the metal while lubricated with said solution, washing the solution from the shaped metal, and app y ng a permanent protective coating to the washed surface.

13. The method which consists in coating 9. surface of iron or steel with a concentrated aqueous solution of an alkali phosphate having a solubility in water of the order of that of di-potassium phosphate, cold working the metal while lubricated with said solution, washing the solution from the shaped surface, and applying a permanent rust-resisting coating to the washed surface. 14. A lubricating material comprising alkali phosphate of the group consisting of dipotassium phosphate, mono-sodium phosphate-and monoammonium phosphate, and a wetting agent capable of reducing the surface tension of water.

15. A lubricating material comprising alkali phosphate of the group consisting of dipotassium phosphate, mono-sodium phosphate and monoammom'um phosphate and hygroscopic material as hygroscopic as glycerine.

16. A lubricating material consisting of a concentrated solution .of (ii-potassium phosphate containing less than 1% of alkaline base sulphonated castor oil soap. 17. A lubricating material for metal consisting of a substantially non-corrosive inorganic salt having a solubility in water of the order of that of dipotassium phosphate and a wetting-agent capable of reducing the surface tension of water.

18. A lubricating material consisting of a concentrated solution of di-potassium phosphate containing not over 1% of highly soluble sulphonated castor oil soap and not over 33% by volume of glycerine.

JOHN L. TUFIS. 

